Constant-on-time converters are known for their fast transient responses, ease of design, and smaller and simpler controllers. Ripple based constant-on-time DC-DC converters utilize a ripple voltage to maintain proper operation with accurate and fast output voltage regulation. A ripple voltage can be generated from sensing inductor current. However, current sensing can require complex circuitry and man not provide a fast transient response and/or good accuracy over a wide range of operating currents.